UNIVERSITY  OF  CALIFORNIA 

AGRICULTURAL  EXPERIMENT  STATION. 
BERKELEY,  CAL. 


E.  W.  HILGARD,  Director.  BULLETIN  No.  108. 


THE  DISTRIBUTION  OF  THE  SALTS 
IN  ALKALI  SOILS. 


AUGUST,  1895. 


THE  DISTRIBUTION  OF  THE  SALTS  IN  ALKALI  SOILS. 

By  E.  W.  Hilgard  and  R.  H.  Loughridge. 


As  time  progresses  the  importance  of  the  alkali  question,  i.  e.,  of 
dealing  successfully  with  the  cultivation  of  lands  more  or  less  impreg- 
nated with  soluble  mineral  salts,  becomes  more  and  more  obvious.  It 
is  to  be  greatly  regretted  that  the  frequent  mistaken  efforts  of  land- 
owners to  suppress,  or  at  least  to  ignore,  this  matter  for  fear  of  injuring 
the  selling  value  of  their  lands,  interpose  additional  difficulties  in  deal- 
ing with  an  intrinsically  sufficiently  difficult  problem.  In  view  of  this 
circumstance,  we  bear  patiently  the  disappointment  we  have  undergone 
in  finding  that,  unexpectedly,  one  of  our  geographically  most  important 
culture  experiment  stations  is  almost  wholly  located  upon  ground  sub- 
ject to  the  difficulties  inherent  in  the  cultivation  of  alkali  land;  since 
we  are  thus  enabled  to  study  the  problem  independently  of  any  private 
interests. 

The  culture  experiment  station  near  the  town  of  Tulare,  originally 
intended  to  represent  the  upper  San  Joaquin  Valley  at  large,  has  thus, 
instead,  become  the  station  for  the  study  of  the  alkali  problem  in  all  its 
phases,  from  the  mildest  to  the  worst.  Until  this  problem  is  solved, 
no  certain  conclusions  for  the  region  at  large  can  be  drawn  from  the 
cultural  results  observed  there;  since  we  now  know  that  all  the  vegeta- 
tion on  the  Station  grounds  is  under  more  or  less  stress  from  the  alkali 
in  the  soil.  If,  however,  we  shall  be  successful  in  overcoming  this 
influence,  as  we  hope  to  be,  the  Station  will  have  rendered,  not  only  to 
the  San  Joaquin  Valley  and  the  State  at  large,  but  to  the  entire  region 
west  of  the  Rocky  Mountains,  a  most  important  service. 

NATURAL    CONDITION   OF    THE    LAND. 

For  an  understanding  of  the  situation,  it  may  be  necessary  to  re-state 
here,  that  in  their  natural  condition  the  lands  of  the  Station,  and  for 
several  miles  around,  as  in  hundreds  of  localities  elsewhere  in  the  val- 
ley and  the  State,  show  only  occasional  alkali  spots;  while  outside  of 
these  spots,  during  the  spring  months,  the  country  is  covered  with  a 
luxuriant  growth  of  native  (largely  annual)  herbaceous  plants,  many 
being  showy  flowers  and  affording  a  most  attractive  sight;  also  proving 
beyond  question  the  great  inherent  fertility  of  the  land.  As  the  season 
advances,  from  April  to  June,  these  plants  go  to  seed  or  dry  up,  leaving 
the  land  more  or  less  bare,  or  with  only  a  sparse  growth  of  hardy, 
drought-resisting,  partially  perennial  plants.  There  is  not,  in  ordinary 
seasons,  any  perceptible  increase  or  decrease  in  the  area  of  the  inter- 
spersed alkali  spots. 

When  such  land  is  put  under  cultivation  without  irrigation  it  will 
in  years  of  unusual  moisture  bring  very  heavy  crops  of  grain,  which 
easily  make  up  for  at  least  one  other  season  of  almost  total  failure, 


when  the  rainfall  is  light  or  unfavorably  distributed.  It  is  this  "  fight- 
ing chance"  of  a  highly  remunerative  crop  that  has  in  so  many  cases 
induced  the  investment  of  entire  fortunes  in  such  ventures,  frequently 
with  a  total  loss,  and  financial  ruin  as  the  result;  a  kind  of  agricultural 
gambling,  little  better  in  itself,  and  with  as  many  chances  against  suc- 
cess, as  that  at  the  faro  table,  but  now  happily  almost  a  thing  of  the 
past. 

BEHAVIOR    UNDER    IRRIGATION. 

With  the  advent  of  the  irrigation  ditch,  the  heavy  grain  crop  becomes 
for  a  few  years  a  matter  of  certainty.  Then  there  is  a  gradual  change 
for  the  worse.  First  it  is  noticed  that  the  alkali  spots  increase  their 
area  outward,  often  merging  neighboring  small  spots  into  one  large  one. 
Then  new  ones  begin  to  appear,  at  first  "no  larger  than  a  man's  hand," 
but  enlarging  each  year,  and  finally  often  so  cutting  up  and  reducing 
the  producing  area,  that  the  land  is  abandoned  in  disgust. 

The  "rise  of  the  alkali"  thus  brought  about  by  irrigation  was  very 
generally  at  first  attributed  (and  sometimes  justly)  to  the  saline  char- 
acter of  the  irrigation  water  used.  But  as  in  time  it  became  apparent 
that  even  the  purest  waters,  such  as  those  of  Kings  and  Kaweah  Rivers, 
would  produce  the  same  result,  the  conclusion  that  the  alkali  salts  are 
simply  brought  up  by  evaporation  from  the  soil  itself,  forced  itself  upon 
the  most  superficial  observers. 

THE    QUESTION   TO   BE    SOLVED. 

Then  arose  the  question,  "  How  much  of  these  salts  does  the  soil  con- 
tain, or  where  do  they  come  from?"  If  it  could  be  shown  that  trie  soil, 
subsoil,  and  substrata  were  equally  impregnated  with  alkali,  and  would 
continue  to  supply  indefinite  amounts  thereof,  the  reclamation  of  such 
lands  for  permanent  cultivation  would  be  almost  hopeless. 

We  at  first  approached  the  problem  by  the  examination  of  "  bottom 
waters"  in  cases  where  the  latter  had  risen  from  a  considerable  depth 
in  consequence  of  a  filling-up  from  leaky  ditches.  It  was  found  that  in 
the  vast  majority  of  cases,  such  water  contained  relatively  small  amounts 
of  alkali  salts  only;  not  more  than  many  waters  successfully  used  for 
irrigation  elsewhere.  It  thus  became  evident  that  the  main  mass  of  these 
salts  exists  in  the  soil  and  subsoil  within  a  short  distance  of  the  surface. 
The  chemical  examination  of  the  "alkali"  moreover  showed  that  it 
consists,  as  a  rule,  of  such  compounds  as  are  known  to  be  formed  in  all 
soils  in  consequence  of  weathering;  and  that  it  contains  all  the  ingre- 
dients useful,  as  well  as  those  useless,  to  plant  growth;  substances  which, 
in  rainy  countries,  are  currently  leached  out  and  carried  into  the  coun- 
try drainage  and  finally  into  the  ocean,  but  which  in  regions  of  scanty 
rainfall  remain  in  the  soil  mass. 

We  are  thus  led  to  the  vitally  important  conclusion  that  the  amount 
of  the  salts  in  these  lands  is  but  limited;  and  that  if  once  removed,  or 
rendered  innocuous  to  crops  in  some  other  way,  it  will  take  thousands 
of  years  in  the  future,  as  in  the  past,  before  another  such  accumulation 
can  occur  from  the  very  gradual  weathering  of  the  soil  mass. 

In  view  of  the  extraordinary  intrinsic  and  permanent  fertility  of 
alkali  lands  when  once  reclaimed,  it  has  seemed  desirable  to  study  in 
detail  the  manner  of  the  distribution  of  the  soluble  salts,  as  well  as  their 


—   5    — 

kind,  at  different  depths  in  the  soil  and  at  different  seasons ;  so  as  to 
gain  an  insight  into  their  migrations  and  transformations,  and  thus  to 
determine  the  best  and  cheapest  methods  of  dealing  with  them. 

The  problem  is  a  very  complex  one  and  involves  a  great  deal  of  labor, 
hence  cannot  be  solved  in  one  or  a  few  seasons,  because  of  the  great 
diversit}r  of  soil  conditions  in  different  localities.  The  investigation 
has  already,  however,  yielded  such  striking  and  practically  important 
results  that  it  seems  best  to  bring  them  to  public  notice  at  once. 

EXAMINATION    OF  SOIL  PROFILES  AND  REPRESENTATION  OF  RESULTS. 

The  obvious  mode  of  determining  the  points  in  question  was  to  sam- 
ple and  examine  the  soil  and  subsoil  at  regular  intervals  of  depth,  in 
spots  representing  the  land  in  its  natural  (unirrigated)  condition  on 
the  one  hand,  and  in  the  irrigated  and  cultivated  on  the  other;  tracing 
the  effects  of  the  latter  conditions  so  definitely  as  to  be  enabled  to  con- 
trol, and  repress  them  where  desirable,  at  the  proper  times  and  by 
suitable  means. 

For  more  ready  understanding  the  results  thus  obtained  are  platted 
so  as  to  show  by  means  of  curves,  or  lines  drawn  from  point  to  point 
of  actual  determination,  the  increase  and  decrease  of  the  total  soluble 
alkali,  as  well  as  of  the  several  salts  composing  it.  As  will  be  seen  on 
the  face  of  the  plates  below,  the  samples  were  taken  (by  means  of  a 
post-hole  auger)  so  that  each  represented  a  vertical  column  of  three 
inches  of  soil;  continuing  thus  to  the  depth  of  two  to  four  feet.  Each  of 
these  samples  was  then  leached  of  its  salts,  and  every  leaching  analyzed 
separately.  It  was  at  first  attempted  to  leach  only  the  average  of  each 
foot,  but  this  proved  quite  unsatisfactory. 

In  the  diagrams  the  depths  are  shown  by  horizontal  lines  at  inter- 
vals of  three  inches,  as  marked  on  the  margin  to  the  left;  while  the 
unbroken  vertical  lines  represent  differences  of  either  two  or  four  hun- 
dredths of  one  per  cent  in  the  saline  contents  of  the  soil  layers,  as 
marked  at  the  top  of  the  diagram;  increasing  from  left  to  right. 

Inasmuch  as  each  sample  represented  the  average  of  three  inches  of 
soil  in  vertical  depth,  in  drawing  the  connecting  lines  or  curves  the 
result  of  the  analysis  is  assumed  to  represent  the  middle  portion  of  each 
three  inches.  Hence,  the  changes  of  direction  always  appear  as  occur- 
ring in  the  middle,  vertically,  of  a  three-inch  space.  The  area  embraced 
between  each  curve  and  the  vertical  line  to  the  extreme  left  represents, 
of  course,  the  aggregate  amount  of  each  ingredient  enumerated,  viz.: 
Common  salt,  Glauber's  salt,  and  sal  soda  as  the  chief  ones,  with  Chile 
saltpeter  (nitrate  of  soda),  also  mentioned  on  account  of  its  fertilizing 
value,  where  present  in  notable  amounts.  The  potash  compounds, 
usually  constituting  from  3  to  7  per  cent  of  the  salts,  are  not  shown 
separately,  being  included  in  the  "Alkali  Sulphate"  curve. 

The  predominance  of  carbonate  of  soda  seen  in  these  diagrams  shows 
at  once  that  the  Tulare  alkali  is  very  "  black,"  so  that  the  use  of  gyp- 
sum to  change  the  carbonate  into  sulphate  is  the  first  thing  needful  in 
attempting  any  reclamation  or  preventive  measures.  But  aside  from 
this,  the  diagrams  suggest,  very  instructively,  the  explanation  of  many 
points  not  well  understood  heretofore. 


—    6    — 

EFFECT    OF    THE    RAINFALL. 

It  is  well  known  to  residents  that  in  Tulare  and  northern  Kern 
Counties  the  greatest  depth  to  which  the  soil  is  wetted  by  the  winter 
rains  rarely  exceeds  three  feet.  This,  then,  is  the  depth  to  which  the 
soluble  salts  in  the  soil  may  be  washed  each  successive  year  by  the  nat- 
ural rainfall;  and  from  this  depth  it  may  partially  or  wholly  reascend 
toward  or  to  the  surface  by  evaporation  during  each  dry  season.  It  is 
reasonable  to  expect  that  near  the  lower  limit  there  will  be  a  gradual 
accumulation  of  the  saline  matters,  which  reach  it  from  above  in  the 
form  of  strong  solutions. 

Plate  1  illustrates  this  strikingly.  It  shows  the  condition  of  the 
natural,  unirrigated  land  at  a  point  half  a  mile  north  of  the  Experi- 
ment Station,  which  was  at  the  time  (May  3,  1895)  covered  by  the 
native  spring  growth  of  herbage  and  flowers,  and  which  during  the  dry 
season  shows  no  sign  of  alkali  on  the  surface.  Evidently,  at  the  time 
represented  here  the  winter  rains  had  washed  the  alkali  salts  so  far 
from  the  surface  down  into  the  subsoil,  that  the  seeds  had  no  difficulty 
in  germinating  near  the  surface;  and  as  the  growing  herbs  covered  the 
ground,  practically  all  the  evaporation  took  place  through  the  roots  and 
leaves,  and  hence  the  alkali  did  not  move  upward  to  any  great  extent. 
The  bulk  of  the  roots  only  reached  to  the  level  (18  to  24  inches),  where 
the  impregnation  is  not  strong  enough  to  hurt  them.  The  soil  moisture 
in  this  upper  layer  being  pretty  nearly  exhausted  by  the  evaporation 
through  the  plants  during  their  growth,  evaporation  from  the  soil  itself 
could  not,  thereafter,  bring  any  perceptible  amount  of  salts  to  the  sur- 
face. Thus  the  first  rain  would,  next  season,  again  enable  the  seeds  to 
germinate  without  injury  from  the  alkali,  despite  the  heavy  impregna- 
tion farther  down;  which  is  seen,  in  this  case,  to  be  greatest  about  the 
second  half  of  the  third  foot. 

As  a  matter  of  course,  not  only  the  native  growth,  but  also  any  crop 
of  which  a  good  stand  has  been  obtained  on  an  alkali  soil,  will  similarly 
tend  to  diminish  or  prevent  the  rise  of  the  alkali.  Hence,  a  crop  of 
alfalfa,  once  established,  may  flourish  for  years  on  ground  that,  so  soon 
as  it  is  left  bare  during  the  dry  season  for  the  fall  sowing  of  a  grain 
crop,  may  prove  altogether  too  strong  near  the  surface,  and  may  kill 
the  grain. 

From  about  the  35-inch  level  down  we  see  a  sudden  and  very  rapid 
decrease  of  the  salts,  so  that  toward  the  end  of  the  fourth  foot  they  are 
reduced  to  little  more  than  is  shown  at  the  end  of  the  first  foot  from 
the  surface. 

Those  familiar  with  "black  alkali"  lands  in  the  upper  San  Joaquin 
Valley  will  at  once  recognize  the  three-foot  depth  as  the  one  at  which, 
in  punching,  or  in  digging  post-holes  or  ditches,  a  very  tough,  intract- 
able, clay  hardpan  is  frequently  encountered,  which,  when  exposed  to 
the  air,  soon  becomes  covered  with  abundance  of  white  salts.  This 
is  the  cause  of  the  thick,  loose  layer  of  salts  often  seen  alongside  of 
irrigation  ditches  in  the  alkali  regions. 

We  see  thus  demonstrated,  beyond  any  possible  cavil,  the  correctness 
of  the  conclusion  we  have  previously  drawn  from  the  examination  of 
the  bottom  waters,  viz.:  that  the  bulk  of  the  alkali  salts  is,  even  in  natural 
alkali  lands,  accumulated  within  easy  reach  of  the  surface  and  of  under- 
drains;  and  that,  if  this  accumulation  is  once  removed,  no  more,  or  at  least 


\   3      I       fc   J      1      1      12.  /\    )j~  \    7r )    3-1     \    *~H  f\  XT      3  0       S3 
Ti'rsL-    V  Fooi-  SeccKi  V  Tool-  ^kird.  \/~Tt 

VeptK      of-    Sifti     Column.      -> 


"Fourth. 


—   8   — 

not  enough  to  do  any  harm,  will  come  from  below.  This  points  to  under- 
drainage  as  the  ready  and  complete  corrective  of  all  alkali,  as  has  been 
long  ago  recommended  by  us. 

But  it  does  not  therefore  follow  that  the  indiscriminate  use  of  under- 
drainage  is  to  be  recommended,  since,  as  we  have  abundantly  shown, 
enormous  amounts  of  valuable  soil  ingredients  would  thus  run  to  waste. 
In  the  majority  of  cases  other  means,  presently  to  be  referred  to,  will 
accomplish  the  reclamation. 

EFFECTS   OF    IRRIGATION. 

Let  us  now  see  what  effect  irrigation,  or  the  establishment  of  leaky 
ditches  in  a  pervious  soil,  will  produce  in  land  circumstanced  as  shown 
in  Plate  1. 

As  regards  the  latter  case,  any  one  can  see  for  himself  that  as  the 
ditch  water,  filling  up  the  land  from  below  upward,  comes  in  contact 
with  the  alkali-sodden  subsoil  or  hardpan  layer,  it  will  dissolve  the 
salts  and  carry  them  up  toward  the  surface.  Evaporation  from  the 
moistened  surface  will  then  go  on  all  the  year  to  a  greater  or  less  extent, 
and  the  alkali  will  keep  steadily  moving  upward;  until,  in  the  course 
of  a  few  years,  the  maximum  will  be  found,  not  three  feet  below,  but 
right  at  the  surface.  This  is  one  phase  of  the  "  rise  of  the  alkali,"  very 
easily  understood  in  the  light  of  Plate  1;  and  its  outcome  is  graphically 
shown  in  Plate  3,  which  scarcely  requires  comment. 

This  diagram  shows  the  condition  of  land  originally  similar  to  that 
represented  by  Plate  1,  which  has  been  irrigated  for  four  or  five  years, 
and,  quite  lately,  has  also  been  influenced  by  a  neighboring  leaky  ditch, 
outside  of  the  Station  inclosure.  Here  we  see  that  the  alkali  has  moved 
bodily  upward,  and  has  accumulated  near  and  at  the  surface  to  such  a 
degree  that  any  useful  growth  of  ordinary  crops  has  become  impossible. 
Seeds  sown  (except  those  of  salt  bushes)  are  quickly  corroded  or 
"rotted"  by  such  alkali  as  this,  and  fail  to  sprout;  anything  set  out, 
ready-grown,  may  live  while  the  rains  last,  but  will  be  promptly  killed 
by  the  corrosion  of  the  root-crown,  or  lower  end  of  the  stem,  from  the 
effect  of  the  strong  solution  formed  around  it  whenever  a  light  rain  or 
heavy  dew  falls,  even  if  the  root  should  be  able  to  resist  the  action  of 
the  alkali  within  the  soil  itself. 

It  is  not  quite  so  easy  to  understand  why  surface  irrigation  should 
produce  the  same  general  result  as  the  rise  of  the  bottom  water  from 
below;  and  yet  a  little  consideration  readily  explains  it.  Under  irriga- 
tion the  land  receives  many  times  more  water  than  in  its  natural 
condition,  but  rarely  enough  to  leach  the  alkali  salts  into  the  country 
drainage,  even  if  the  impervious  hardpan  layer  did  not  stand  in  the 
way.  Practically  all  this  irrigation  water  therefore  ultimately  evapo- 
rates in  the  course  of  the  year.  As  it  penetrates  the  soil  to  a  greater 
depth  than  the  natural  rainfall  ever  goes,  it  gradually  dissolves  the 
alkali  salts  in  the  subsoil,  and  in  the  progress  of  its  evaporation 
throughout  the  season,  carries  them  with  it  toward  the  surface,  instead 
of  leaving  most  of  them  accumulated  at  between  two  and  three  feet 
depth,  as  in  the  natural  state.  In  the  course  of  time,  especially  in 
orchards  where  the  soil  remains  bare  and  therefore  exposed  to  evapora- 
tion throughout  the  season,  the  accumulation  near  the  surface  becomes 
so  great  as  to  injure  even  the  bark  of  full-grown  trees  and  vines ;  while 


—    9    — 


Dej?rk     <jf-   SoLL    0>Lu.Y*.n. 


\rCh\J  Foot 


—  10  — 


t 

o        CO 

"3       £ 


a. 


Depth.     of-  Soil  Col 


S  " 

i 

2 

'■~\ 

— 

o 

•t 

)5» 

-"- 

«' 

— 

3  ■*• 

^*- 

— 

"♦- 

Z 

i 

i 

* 

J 

*-3     S 

% 

3 

US 

s!    ^  ^    Z 

o 

J 
Si 

'-( 

<s 

,5  If 

<j  — - 

^ 
5 

u„„. 

S 

*   f9 

t>M.7L   -> 


Depict.    o|r  Soil     Colu-vM-ri-3  -? 


—  11  — 

ordinary  herbaceous  vegetation  becomes  impossible.  If  the  alkali  should 
be  of  the  "black"  kind — i.  <?.,  carbonate  of  soda— the  soil  will  soon 
begin  to  settle,  and  puddles  of  inky  water  will  remain  for  some  time 
after  rains  or  irrigation  ;  sometimes  forming  permanent  "  alkali  ponds/' 
with  a  bottom  of  tough,  impervious  hardpan,  of  the  same  nature  as  that 
shown  in  Plate  1. 

That  these  worst  effects  can  be  suppressed  by  the  conversion  of 
"  black  "  alkali  into  "  white,"  by  means  of  gypsum,  has  been  already 
sufficiently  explained  in  former  publications.  The  "  white  "  or  neutral 
alkali  is  many  times  less  injurious  than  the  "black,"  which  is  so  cor- 
rosive that  it  dissolves  not  only  the  humus  of  the  soil,  but  also  the  bark 
of  plants;  always  excepting  the  wonderful  "  salt  bushes  "  and  their  kind. 
But  there  are  limits,  varying  for  different  plants,  beyond  which  even 
the  "white"  alkali  becomes  incompatible  with  cultivation  ;  so  that  its 
accumulation  near  the  surface  must  always  be  prevented  as  much  as 
possible.  Diagram  No.  3  shows  the  condition  of  bare  irrigated  land  in 
May  ;  at  the  end  of  the  dry  season,  we  find  nearly  the  whole  of  the 
alkali  concentrated  within  six  inches  of  the  surface,  as  is  shown  by 
diagrams  Nos.  4a  and  46.  These  diagrams  show  strikingly  that  if  we  could 
afford  to  remove  that  first  six  inches  of  soil,  we  would  have  no  more 
trouble  from  alkali ;  but  at  the  same  time,  we  would  have  seriously 
damaged  the  land's  productiveness. 

EFFECTS    OF    CROPPING. 

Plate  2  shows  the  effect  of  a  growing  crop  on  the  same  land  as  that 
in  Plate  3,  within  the  Station  grounds,  the  samples  on  the  two  plates 
having  been  taken  within  ten  feet  of  each  other.  But  a  heavy  dressing 
of  gypsum  had  been  applied  where  2a  and  26  were  taken,  with  good 
irrigation;  and  barley  was  sown  in  January,  1895.  Some  rather 
abundant  rains  fell  afterward,  which  naturally  leached  the  alkali  salts 
away  from  the  surface,  so  as  to  leave  it  quite  weak  within  the  first  foot. 
Evidently,  the  barley  germinated  and  made  its  first  growth  under  these 
conditions.  But*  as  it  failed  to  cover  the  ground  fully,  some  surface 
evaporation  took  place  and  the  alkali  began  an  upward  movement,  the 
effect  of  which,  in  the  increase  of  salts  at  the  surface,  is  seen  in  both 
figures  (2a  and  26),  but  modified,  in  the  latter  one,  by  the  contrary  effect 
of  a  light  late  rain,  which  diminished  somewhat  the  salts  at  the  sur- 
face. These  two  profiles  are  clearly  the  transition  phase  between  the 
natural  condition  of  the  land  as  shown  in  Plate  1,  and  that  of  a  bare 
alkali  spot  as  exemplified  in  Plate  3;  and  illustrates  well  the  effect  pro- 
duced upon  evaporation,  and  the  consequent  movement  of  the  alkali 
salts,  even  by  a  cereal  crop,  with  its  shallow  roots  and  thin  foliage. 
It  is  obvious  that  a  crop  of  alfalfa,  once  established  upon  this  land,  and 
bringing  to  bear  upon  it  the  action  of  its  deep  roots  and  dense  shade, 
would,  by  the  repression  of  surface  evaporation,  tend  to  restore  the 
natural  condition  as  shown  in  Plate  1. 


—  12  — 


3 

. 

1 

/\ 

•^ 

•1 

A 

•  2" 

n» 

/ 

V 

....... 

Si 

3 

V 

rt 

>*- 

2j 

"l 

,    ft 

"1 



.* 

■•••*•■•■ 

»n\ 

. a 

«      IP 

a 

7     V 

4 

S'3 

/ 

/ 

.....^ 

f 

V._ 

/ 

"  © 

4\ 

<y. 

y 

1 

v  " 

<n\ 

u 

V  ■•>*'• 

-■- 

<J 

->\ 

^y 

■3P 

*■ 

"S 

*< 

A 

\ 

\ 

"■orjV  ' 

\ 

\ 

y 

s 

"6\ 

- 

\ 

\  X 

"V 

L 

» 

k 

83. 

|\ 

A 

-J 

\ 

\ 

/  \ 

\       i 

\  / 

\ 

* 

A    / 

.      +    < 

* 

\/ 

,  +* 

v. 

■*>•* 

\ 

N^\ 

V,. 

,*•* 

^ 

I.I.T.. 

'"*""' 

*......., 

! 

..**>. 

**$■* 

"T" 

'"13 

"±"*c 

\   0 

6 

9 

/■«-/ 

^    «" 

/*- 

XI 

'^/ 

\f/ 

30 

r    jj    i   JL  J 

7/ 

m/-    v 

'  Too 

/- 

-Stc 

unJ 

»   7-oi 

»/- 

7VW*    ^  ?r««/'- 

a  Jo 

5  .! 

•s  *. 

t>  a. 


W 


TiysI-     ^    Foe/-  -S<*««.«*  V^ 

De/jfii     of-rSotL     Colum-ii  — > 


;f<>W- 


Too-trh.'-^F^F 


—  13  — 

COUNTERACTING  EVAPORATION. 

From  what  has  been  said  it  is  obvious  that  since  evaporation  from  the 
soil  surface  is  the  cause  of  any  u  rise  of  the  alkali"  one  of  the  chief  pre- 
ventive measures  must  be  the  reduction  of  surface  evaporation  to  the 
lowest  possible  point.  This  can  be  done  either  by  mulching  or,  less 
effectually,  by  shading. 

The  best  mulch,  available  in  all  cases,  is  a  well  and  deeply  tilled  sur- 
face soil,  on  which  a  crust  is  never  allowed  to  form.  Then  evaporation 
will  be  reduced  to  the  minimum,  and  whatever  does  take  place  leaves 
the  alkali  distributed  through  the  whole  of  the  tilled  layer,  instead  of 
at  the  surface,  where  the  bulk  of  the  damage  is  usually  done.  For,  a 
loosely  tilled  soil  will  take  up  little  or  no  moisture  from  a  denser  or 
more  compact  subsoil,  which  it  protects  quite  as  effectually  as  would  a 
straw  mulch. 

Of  course,  the  depth  or  thickness  of  this  protective  tilled  layer  is  of 
the  utmost  importance,  not  only  for  the  sake  of  preventing  evaporation 
and  accumulation,  but  also  because,  since  the  maximum  of  alkali  in 
irrigated  land  at  the  end  of  the  dry  season  is  always  near  the  surface, 
the  intermixing  of  the  strong  surface  alkali  with  as  large  a  mass  of 
subsoil  as  possible,  is  important  in  order  to  dilute  and  diffuse  it;  so  that 
it  may  not  be  strong  enough  anywhere  to  hurt  the  roots  or  root-crown. 
After  such  an  intermixture,  say  to  the  depth  of  ten  or  twelve  inches,  it 
takes  some  time  to  bring  the  salts  to  the  surface  again  to  a  sufficient 
extent  to  hurt  the  crop.  An  instinctive  recognition  of  this  principle 
has  led  cultivators  of  alkali  soils  in  some  cases  to  resort  to  sanding  the 
surface,  and  with  temporary  good  results. 

But  the  mainstay  in  the  cultivation  of  alkali  land  must  always  be 
the  maintenance  of  deep  and  loose  tilth  throughout  the  times  when  evapora- 
tion is  active.  This  implies  the  growing  on  them  of  hoed  rather  than 
grain  crops,  unless  drill  culture  (which  at  present  prices  would  hardly 
pay)  were  resorted  to.  The  growing  of  corn,  beans,  beets,  and  possibly 
of  canaigre,  always  choosing  preferably  the  deep-rooted  crops,  is  there- 
fore indicated;  and  experience  at  Chino  has  conclusively  shown  that 
the  very  best  of  beets  may  be  grown  on  light  alkali  soils  in  which  com- 
mon salt  is  not  too  prominent. 


Deep  and  loose  tillage,  however,  is  practically  impossible  on  lands 
tainted  with  any  considerable  amount  of  "black"  alkali.  It  will  remain 
cloddy,  and  will  crust  over  even  with  dew,  despite  all  cultivating,  har- 
rowing, and  clod-crushing.  The  first  need,  therefore,  is  the  neutraliza- 
tion of  the  black  alkali  with  gypsum,  by  which  operation  other  important 
benefits  are  also  secured.  The  saving  in  cost  of  cultivation  on  heavier 
lands  will  alone  soon  pay  for  the  purchase  of  the  gypsum,  aside  from 
increased  and  improved  products.  It  must  always  be  remembered  that 
little  or  no  benefit  is  to  be  expected  from  gypsum  in  cases  of  purely 
<; white,"  neutral  alkali;  but  there  are  tens  of  thousands  of  acres  of 
land  now  lying  idle,  lightly  tainted  with  "black"  alkali,  that  would  be 
definitely  reclaimed,  and  rendered  profusely  productive,  by  the  use, 
once  for  all,  of  a  ton  of  gypsum  per  acre.  But  it  is  not  absolutely 
necessary  to  use  the  entire  amount  at  once;  it  can  also  be  done  by 


—  14  — 

annual  installments  of  say  five  hundred  pounds  per  acre,  put  in  some 
time  before  the  seed.  The  latter  will  thus  be  protected  from  being 
killed  by  the  black  alkali,  and  secure  a  stand  to  shade  the  ground, 
preventing  an  injurious  rise  of  salts  for  the  season  at  least.  It  must  be 
remembered,  however,  that  gypsum  cannot  act  on  alkali  without  water; 
and  that  the  action  itself  takes  several  weeks  before  immunity  is  secured, 
and  continues  for  several  months,  and  even  longer. 

The  dressing  of  gypsum  should  therefore  be  applied  in  ample  time 
before  seeding,  and  after  cultivating  or  plowing-in  should  be  promptly 
followed  by  irrigation,  unless  the  rainy  season  can  be  relied  upon  to 
perform  the  service  before  seeding  time.  The  smaller  the  seed  to  be 
sown  the  more  important  is  this  precaution;  beans,  peas,  or  maize  may 
remain  unharmed  where  alfalfa,  or  other  clover  seeds,  as  well  as  those 
of  meadow  and  pasture  grasses,  would  perish  either  before  or  during 
germination. 

One  additional  point  should  be  emphasized  here.  It  will  be  seen 
from  the  curve  lines  representing  the  individual  salts — common  and 
Glauber's  salt,  and  sal  soda — that  the  latter  is  proportionally  most 
abundant  in  the  clay  hardpan  (Plate  1),  where  it  forms  from  80  to  over 
90  per  cent  of  the  whole;  while  near  the  surface,  in  the  very  same  bore- 
hole, it  forms  about  23  per  cent  only.  This  is  due  to  the  moisture  and 
want  of  aeration  in  the  subsoil,  acting  in  a  manner  not  easily  explained 
in  a  popular  way.  But  it  may  be  taken  for  granted  that  whenever  an 
alkali  soil  is  subjected  to  the  action  of  stagnant  water,  or  of  abundant 
moisture  without  aeration,  the  formation  of  black  alkali  will  take  place. 
This  is  the  reason  why  the  latter  is  most  commonly  found  in  low,  moist 
ground,  and  in  close,  heavy  soils;  while  on  the  higher  ground  adjacent 
the  white  salts  alone  may  prevail.  The  "  swamping  "  of  alkali  lands  is 
thus  seen  to  be  doubly  pernicious;  and  the  leaky  ditches  which  cause  it 
should,  for  this  reason  alone,  be  considered  a  public  nuisance. 


